Control device and control method for vehicle

ABSTRACT

When an automatic transmission is shifted from neutral to a a forward gear, an ECU calculates the appropriate target gear. If the target gear speed is the second forward gear or higher, a target command pressure of a first engagement element is immediately increased to a maximum pressure regardless of an input torque, and a target command pressure of a second engagement element is gradually increased in accordance with the input torque.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2008-158273 filed onJun. 17, 2008 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to control device and a control method fora vehicle equipped with an automatic transmission. More specifically,the present invention relates to a vehicle control for switching a shiftlever position selected by the driver from a neutral position to aforward drive position.

2. Description of the Related Art

In a vehicle equipped with an automatic transmission, the driver maymove the shift lever in order to change shift lever position from aneutral position (referred to as an “N position” below) to a forwarddrive position (referred to as a “D position” below), which will bereferred to as an “N/D operation” below. Friction engagement elementsthat were released are consequently engaged such that the automatictransmission switches from neutral to the D-range. Significant shiftshock may be generated if the driver depresses the accelerator pedalimmediately after performing an N/D operation. Art for suppressing suchshift shock is described in Japanese Patent Application Publication No.JP-A-61-105228, for example.

The control device for an automatic transmission described inJP-A-61-105228 includes: a shift operation sensor that detects anoperation to shift from a stop range to a running range; a vehicle speedsensor that detects a vehicle speed; an engine speed sensor that detectsan engine speed; and an output torque reduction unit that reduces theengine output torque alongside a transition to engaging a running-rangefriction engagement device when there is an operation to shift from thestop range to the running range while the vehicle speed is equal to orless than a predetermined vehicle speed, and when the engine speedbecomes equal to or greater than a predetermined engine speed within apredetermined time since the shift operation.

According to the control device for an automatic transmission describedin JP-A-61-105228, if the driver attempts to perform a shift operationand immediately start moving the vehicle (that is, when there is anoperation to shift from the stop range to the running range while thevehicle speed is equal to or less than a predetermined vehicle speed,and the engine speed becomes equal to or greater than a predeterminedengine speed within a predetermined time since the shift operation) theengine output torque is reduced when engaging the D-range frictionengagement device. Therefore, the torque borne by the D-range frictionengagement device upon engagement thereof is kept within a tolerancevalue and sudden fluctuations in the output shaft torque of theautomatic transmission upon engagement of the D-range frictionengagement device are suppressed. The shift shock and shock load canthus be alleviated. There is also no need to delay the engagement of therunning-range friction engagement device, so a delay in starting vehicletravel may be avoided.

However, if the above N/D operation is performed while the vehicle is inmotion, it may be necessary to engage two friction engagement elementsin order to form a gear higher than the forward first gear. If theaccelerator pedal is depressed immediately after performing the N/Doperation, leads to the engagement of the friction engagement elements,as well as an increase in the torque input to the friction engagementelements. Accordingly, the hydraulic pressure to the friction engagementelements must also be increased in order to prevent slipping of thefriction engagement elements. This may consequently generate engagementshock due to the imbalance between the engagement state of one frictionengagement element and the engagement state of the other frictionengagement element.

In order to appropriately suppress such engagement shock, until thefriction engagement elements are completely engaged, the output torqueof a drive source (an input torque of the automatic transmission) may bedecreased considerably more than when only one friction engagementelement is engaged. However, this means that the vehicle does notaccelerate even though the accelerator is being depressed, and gives thedriver a sense of incongruity.

JP-A-61-105228 and Japanese Patent Application Publication No.JP-A-2003-287122 do not provide any solution to the above problem.

SUMMARY OF THE INVENTION

The present invention provides a control device and a control methodthat suppress engagement shock while realizing travel in line with adriver's intent when the automatic transmission is shifted from neutralinto a drive gear.

A control device for a vehicle according to a first aspect of thepresent invention, wherein the vehicle includes a plurality ofengagement elements that is released when a shift lever position is in aneutral position; a hydraulic circuit that controls a hydraulic pressureof oil fed to the plurality of engagement elements; and an automatictransmission that changes a speed of and outputs a rotation of a drivesource, the control device including: a determination unit thatdetermines whether the shift lever position has been changed from theneutral position to a forward running position; a torque reduction unitthat controls the drive source such that an output torque of the drivesource is lower than a torque in accordance with an accelerator opening,if the determination unit determines that the shift lever position hasbeen changed to the forward running position; a calculation unit thatcalculates a target gear speed in accordance with a vehicle speed, if itis determined by the determination unit that the shift lever positionhas been changed to the forward running position; and a control unitthat controls the hydraulic circuit such that a first engagement elementthat is part of the two or more engagement elements is engaged beforeengagement of a second engagement element, if the target gear speedcalculated by the calculation unit is a gear speed formed by engaging atleast two or more engagement elements.

In addition to the configuration of the first aspect, the control unitmay increase a hydraulic pressure fed to the first engagement element toa predetermined hydraulic pressure, and then increase a hydraulicpressure fed to the second engagement element,

Further, the control unit may set such that a time elapsed from the whenthe hydraulic pressure fed to the first engagement element startsincreasing until a maximum pressure is reached is shorter than a timeelapsed from when the hydraulic pressure fed to the second engagementelement starts increasing until a maximum pressure is reached.

The control unit may also increase the hydraulic pressure fed to thefirst engagement element regardless of an input torque that is inputfrom the drive source to the automatic transmission, and increase thehydraulic pressure fed to the second engagement element in accordancewith the input torque.

If the two or more engagement elements are a combination of a primaryengagement element through which the input torque is output from theautomatic transmission even if singly engaged, and a secondaryengagement element through which the input torque from the automatictransmission is not output if singly engaged, the control unit mayimmediately increase a hydraulic pressure fed to the secondaryengagement element to a maximum pressure regardless of the input torque,and increase a hydraulic pressure fed to the primary engagement elementin accordance with the input torque.

If the two or more engagement elements are a combination of primaryengagement elements through which the input torque is output from theautomatic transmission even if singly engaged, the control unit mayincrease a hydraulic pressure fed to part of the primary engagementelements in a preset manner regardless of the input torque, and increasea hydraulic pressure fed to the remaining primary engagement elements inaccordance with the input torque.

A control method for a vehicle according to a second aspect of thepresent invention, wherein the vehicle includes a plurality ofengagement elements that is released when a shift lever position is in aneutral position; a hydraulic circuit that controls a hydraulic pressureof oil fed to the plurality of engagement elements; and an automatictransmission that changes a speed of and outputs a rotation of a drivesource, the control method including: determining whether the shiftlever position has been changed from the neutral position to a forwardrunning position; controlling the drive source such that an outputtorque of the drive source is lower than a torque in accordance with anaccelerator opening, if it is determined that the shift lever positionhas been changed to the forward running position; calculating a targetgear speed in accordance with a vehicle speed, if it is determined thatthe shift lever position has been changed to the forward runningposition; and controlling the hydraulic circuit such that a firstengagement element that is part of the two or more engagement elementsis engaged before engagement of a second engagement element, if thetarget gear speed is a gear speed formed by engaging at least two ormore engagement elements. The second aspect of the present invention mayinclude the same conditions as the first aspect described above.

According to the first and second aspects of the present invention, ifthe driver changes the shift lever position from the neutral position toa forward running position, and the target gear speed calculated inaccordance with the vehicle speed is a gear speed formed by engagementat least two or more engagement elements, the first engagement elementthat is part of the two or more engagement elements is engaged beforeengagement of the second engagement element. Accordingly, fluctuationsin the balance between the engagement state of the first engagementelement and the engagement state of the second engagement element can besuppressed. It is therefore possible to suppress engagement shockwithout excessively lowering an output torque of the drive source. As aconsequence, travel in line with the driver's intent can be achievedwhere the vehicle is accelerated in accordance with the depression ofthe accelerator while suppressing engagement shock.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further features and advantages of the invention willbecome apparent from the following description of example embodimentswith reference to the accompanying drawings, wherein like numerals areused to represent like elements and wherein:

FIG. 1 is a schematic structural diagram that shows a power train of avehicle;

FIG. 2 is a skeleton diagram that shows a planetary gear unit of anautomatic transmission;

FIG. 3 shows an operational chart of the automatic transmission;

FIG. 4 shows a hydraulic circuit of the automatic transmission;

FIG. 5 is a functional block diagram of an ECU;

FIG. 6A and FIG. 6B are a flowchart that shows the control structure ofa program executed by the ECU; and

FIG. 7 is a timing chart for a target command pressure of a firstengagement element and a target command pressure of a second engagementelement controlled by the ECU.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described below withreference to the accompanying drawings. Like elements are represented bylike reference numerals, and the names and functions of such elementsare identical. For this reason, repeated detailed descriptions of theseelements will not be given below.

A vehicle equipped with a control device according to an embodiment ofthe present invention will be explained with reference to FIG. 1. Thevehicle shown is a front-engine rear-drive (FR) vehicle, but the controldevice may also be used in a non-FR vehicle.

The vehicle includes an engine 1000, an automatic transmission 2000, atorque converter 2100, a planetary gear unit 3000 that forms part of theautomatic transmission 2000, a hydraulic circuit 4000 that forms part ofthe automatic transmission 2000, a propeller shaft 5000, a differentialgear 6000, rear wheels 7000, and an electronic control unit (ECU) 8000.The control device according to the present embodiment may beimplemented by executing a program stored in a read-only memory (ROM) ofthe ECU 8000, for example.

The engine 1000 is an internal combustion engine that combusts a mixtureof air and fuel injected from injectors (not shown) inside a combustionchamber of a cylinder. The combustion presses down a piston inside thecylinder, which rotates a crankshaft. An auxiliary device 1004 such asan alternator and an air conditioner are driven by the driving force ofthe engine 1000. Note that a motor may also be used as a drive source inaddition to or in place of the engine 1000.

The automatic transmission 2000 is connected with the engine 1000 viathe torque converter 2100. The automatic transmission 2000 forms adesired gear speed in order to shift a rotational speed of thecrankshaft to a desired rotational speed. The driving force output fromthe automatic transmission 2000 is transmitted to the right and leftrear wheels 7000 via the propeller shaft 5000 and the differential gear6000.

The ECU 8000 is connected via a harness, for example, with a vehiclespeed sensor 8002; a position switch 8006 of a shift lever 8004; anaccelerator operation amount sensor 8010 of an accelerator pedal 8008; adepression force sensor 8014 of a brake pedal 8012; a throttle openingsensor 8018 of an electronic throttle valve 8016; an engine speed sensor8020; an input shaft speed sensor 8022, and an output shaft speed sensor8024.

The vehicle speed sensor 8002 detects a vehicle speed V based on therotational speed of a drive shaft 6100. The position switch 8006 detectsthe position (a shift position) SP of the shift lever 8004. Theaccelerator operation amount sensor 8010 detects the operation amountACC of the accelerator pedal 8008. The depression force sensor 8014detects the depression force on the brake pedal 8012. The throttleopening sensor 8018 detects the throttle opening amount TH of theelectronic throttle valve 8016. The engine speed sensor 8020 detects thecrankshaft speed (an engine speed) NE. The input shaft speed sensor 8022detects the input shaft speed (a turbine speed of the torque converter2100) NT of the automatic transmission 2000. The output shaft speedsensor 8024 detects the rotational speed (an output shaft speed) NOUT ofthe output shaft of the automatic transmission 2000. These sensors sendsignals that represent the detection results to the ECU 8000.

The ECU 8000 controls various devices such that the vehicle achieves adesired running state based on maps and programs stored in the ROM, andthe signals sent from the vehicle speed sensor 8002, the position switch8006, the accelerator operation amount sensor 8010, the depression forcesensor 8014, the throttle opening sensor 8018, the engine speed sensor8020, the input shaft speed sensor 8022, the output shaft speed sensor8024, and the like.

According to the present embodiment, when the shift lever 8004 is in theD position, the D range of the automatic transmission is selected.Accordingly, the ECU 8000 controls the automatic transmission 2000 suchthat any gear speed among a forward first to eighth speeds is formed.The automatic transmission 2000 is capable of transmitting a drivingforce to the rear wheels 7000 based on the gear speed formed among theforward first to eighth speeds. Note that in the D range, it may also bepossible to form a higher gear speed than eighth speed.

The ECU 8000 calculates a target gear based on a shift diagram, which isprepared beforehand from testing or the like using the vehicle speed Vand the accelerator operation amount ACC as parameters, and controls theautomatic transmission 2000 to form the calculated target gear. Notethat the shift diagram is at least set such that a higher target gear iscalculated for a faster vehicle speed V.

Although the ECU 8000 is described as one unit in the presentembodiment, the ECU 8000 may be divided into two or more units. Forexample, the ECU 8000 may be configured to include an engine ECU thatcontrols the engine 1000 and an electronic control transmission (ECT)ECU that controls the automatic transmission 2000, with the engine ECUand the ECT ECU capable of sending and receiving signals to and from oneanother.

The planetary gear unit 3000 will be explained next with reference toFIG 2. The planetary gear unit 3000 is connected with the torqueconverter 2100, which has an input shaft 2102 that is coupled with thecrankshaft.

The planetary gear unit 3000 includes a front planetary gear set 3100, arear planetary gear set 3200, a C1 clutch 3301, a C2 clutch 3302, a C3clutch 3303, a C4 clutch 3304, a B1 brake 3311, a B2 brake 3312, and aone-way clutch (F) 3320.

The front planetary gear set 3100 is a double-pinion planetary gearmechanism. The front planetary gear set 3100 includes a first sun gear(S1) 3102, a pair of first pinion gears (P1) 3104, a first carrier (CA)3106, and a first ring gear (R) 3108.

The first pinion gear (P1) 3104 meshes with the first sun gear (S1) 3102and the first ring gear (R) 3108. The first carrier (CA) 3106 supportsthe first pinion gear (P1) 3104 such that the first pinion gear (P1)3104 is capable of orbiting and rotating.

The first sun gear (S1) 3102 is fixed to the gear case 3400 and heldstationary. The first carrier (CA) 3106 is coupled with an input shaft3002 of the planetary gear unit 3000.

The rear planetary gear set 3200 is a Ravigneaux planetary gearmechanism. The rear planetary gear set 3200 includes a second sun gear(S2) 3202, a second pinion gear (P2) 3204, a rear carrier (RCA) 3206, arear ring gear (RR) 3208, a third sun gear (S3) 3210, and a third piniongear (P3) 3212.

The second pinion gear (P2) 3204 meshes with the second sun gear (S2)3202, the rear ring gear (RR) 3208, and the third pinion gear (P3) 3212.The third pinion gear (P3) 3212 meshes with the third sun gear (S3)3210, in addition to the second pinion gear (P2) 3204.

The rear carrier (RCA) 3206 supports the second pinion gear (P2) 3204and the third pinion gear (P3) 3212 such that the second pinion gear(P2) 3204 and the third pinion gear (P3) 3212 are capable of orbitingand rotating. The rear carrier (RCA) 3206 is coupled with the one-wayclutch (P) 3320. The rear carrier (RCA) 3206 is held stationary when thetransmission is in first gear (during running that uses the drivingforce output from the engine 1000). The rear ring gear (RR) 3208 iscoupled with an output shaft 3004 of the planetary gear unit 3000.

The one-way clutch (F) 3320 is provided in parallel with the B2 brake3312. Namely, an outer race of the one-way clutch (F) 3320 is fixed tothe gear case 3400, and an inner race of the one-way clutch (F) 3320 iscoupled with the Tear carrier (RCA) 3206.

The C1 clutch 3301 and the C2 clutch 3302 are friction engagementelements (referred to as “primary engagement elements” whereappropriate), and torque input to the input shaft 3002 (referred tosimply as “input torque” below) is output to the output shaft 3004through the independent engagement of the C1 clutch 3301 and the C2clutch 3302.

The C3 clutch 3303, the C4 clutch 3304, the B1 brake 3311, and the B2brake 3312 are friction engagement elements (referred to as “secondaryengagement elements” where appropriate) that are subjected to a reactionforce when one of the primary engagement elements is engaged; inputtorque is not output to the output shaft 3004 through only their singleengagement.

FIG. 3 shows an operation chart that expresses the relationship betweenthe transmission gear speeds and the operation states of the clutchesand brakes. The first to eighth forward gears and first and secondreverse gears are formed by operating the brakes and clutches accordingto the combinations indicated in the operation chart.

To form the first forward gear, as shown in FIG. 3, the ECU 8000 engagesthe C1 clutch 3301, which is a primary engagement element, and releasesthe other clutches and brakes.

To form the second forward gear, for example, the ECU 8000 engages theC1 clutch 3301, which is a primary engagement element, and the B1 brake3311, which is a secondary engagement element, and releases the otherclutches and brakes.

To form the fifth forward gear, for example, the ECU 8000 engages the C1clutch 3301 and the C2 clutch 3301, which are both primary engagementelements, and releases the other clutches and brakes.

The hydraulic circuit 4000 will be explained next with reference to FIG4. However, it should be noted that the hydraulic circuit 4000 is notlimited by the description below.

The hydraulic circuit 4000 includes an oil pump 4004, a primaryregulator valve 4006, a manual valve 4100, a solenoid modulator valve4200, an SL1 linear solenoid (also referred to as SL(1) below) 4210, anS12 linear solenoid (also referred to as SL(2) below) 4220, an SL3linear solenoid (also referred to as SL(3) below) 4230, an SL4 linearsolenoid (also referred to as SL(4) below) 4240, an SL5 linear solenoid(also referred to as SL(5) below) 4250, an SLT linear solenoid (alsoreferred to as SLT below) 4300, and a B2 control valve 4500.

The oil pump 4004 is coupled with the crankshaft of the engine 1000.Rotation of the crankshaft drives the oil pump 4004 to thereby generatehydraulic pressure.

The hydraulic pressure generated by the oil pump 4004 is adjusted to aline pressure by the primary regulator valve 4006. The primary regulatorvalve 4006 operates using a throttle pressure adjusted by the SLT 4300as a pilot pressure. Oil at the line pressure is fed to the manual valve4100 via a line pressure oil passage 4010.

The manual valve 4100 includes a drain port 4105. Oil is discharged fromthe drain port 4105 to a D-range pressure oil passage 4102 and anR-range pressure oil passage 4104.

When a spool of the manual valve 4100 is set to the D position, the linepressure oil passage 4010 is communicated with the D-range pressure oilpassage 4102, and oil having the D-range pressure is fed to the D-rangepressure oil passage 4102. At such time, the R-range pressure oilpassage 4104 is communicated with the drain port 4105, and the oil inthe R-range pressure oil passage 4104 is discharged from the drain port4105.

When the spool of the manual valve 4100 is set to the R position, theline pressure oil passage 4010 is communicated with the R-range pressureoil passage 4104, and oil having the R-range pressure is fed to theR-range pressure oil passage 4104. At such time, the D-range pressureoil passage 4102 is communicated with the drain port 4105, and oilhaving the D-range pressure of the D-range pressure oil passage 4102 isdischarged from the drain port 4105.

When the spool of the manual valve 4100 is set to the N position, boththe D-range pressure oil passage 4102 and the R-range pressure oilpassage 4104 are communicated with the drain port 4105. Oil having theD-range pressure of the D-range pressure oil passage 4102 and oil havingthe R-range pressure of the R-range pressure oil passage 4104 are thendischarged from the drain port 4105.

The B2 control valve 4500 selectively feeds oil from either the D-rangepressure oil passage 4102 or the R-range pressure oil passage 4104 tothe B2 brake 3312. The B2 control valve 4500 is connected with theD-range pressure oil passage 4102 and the R-range pressure oil passage4104. The B2 control valve 4500 is controlled by a biasing force of aspring and oil fed from an SLU solenoid valve (not shown).

If the SLU solenoid valve is on, the B2 control valve 4500 is set to thestate shown on the left side of FIG. 4. In such case, the B2 brake 3312is supplied with oil pressurized to the D-range pressure, with thehydraulic pressure of oil supplied from the SLU solenoid valve used asthe pilot pressure. It should be noted that oil supplied to the D-rangepressure oil passage 4102 is ultimately fed to the C1 clutch 3301, theC2 clutch 3302, and the C3 clutch 3303.

If the SLU solenoid valve is off, the B2 control valve 4500 is set tothe state shown on the right side of FIG. 4. In such case, the B2 brake3312 is supplied with oil at the R-range pressure of the R-rangepressure oil passage 4104.

The SL(1) 4210, the SL(2) 4220, the SL(3) 4230, the SL(4) 4240, and theSL(5) 4250 are normally-closed linear solenoid valves. The outputhydraulic pressure of the linear solenoid valves is controlled by drivecurrents I, which serve as drive signals, output from the ECU 8000 tothe respective linear solenoid valves. In other words, the outputhydraulic pressure of the linear solenoid valves is at a minimum (“0”)when no current is conducted, with the output hydraulic pressureincreases as the drive currents I from the ECU 8000 increase.

The hydraulic pressure of oil fed to the C1 clutch 3301 is adjusted bythe SL(1) 4210. The hydraulic pressure of oil fed to the C2 clutch 3302is adjusted by the SL(2) 4220. The hydraulic pressure of oil fed to theC3 clutch 3303 is adjusted by the SL(3) 4230. The hydraulic pressure ofoil fed to the C4 clutch 3304 is adjusted by the SL(4) 4240. Thehydraulic pressure of oil fed to the B1 brake 3311 is adjusted by theSL(5) 4250.

Based on the input torque and the like, the ECU 8000 respectivelycalculates a target command pressure P(C1) of the C1 clutch 3301, atarget command pressure P(C2) of the C2 clutch 3302, a target commandpressure P(C3) of the C3 clutch 3303, a target command pressure P(C4) ofthe C4 clutch 3304, and a target command pressure P(B1) of the B1 brake3311.

The ECU 8000 outputs a drive current I(C1) that corresponds to thetarget command pressure P(C1), a drive current I(C2) that corresponds tothe target command pressure P(C2), a drive current I(C3) thatcorresponds to the target command pressure P(C3), a drive current I(C4)that corresponds to the target command pressure P(C4), and a drivecurrent I(B1) that corresponds to the target command pressure P(B1) tothe SL(1) 4210, the SL(2) 4220, the SL(3) 4230, the SL(4) 4240, and theSL(5) 4250, respectively.

With the line pressure as a source pressure, the solenoid modulatorvalve 4200 adjusts the hydraulic pressure (a solenoid modulatorpressure) of oil that is fed to the SLT 4300 to a prescribed pressure.

The SLT 4300 adjusts the solenoid modulator pressure and adjusts the oilto the throttle pressure in accordance with the drive current I(T) fromthe ECU 8000, which is based on the accelerator operation amount ACCdetected by the accelerator operation amount 8010 and the like. Oil atthe throttle pressure is fed to the primary regulator valve 4006 via anSLT oil passage 4302. The throttle pressure is used as a pilot pressurefor the primary regulator valve 4006.

In a vehicle having the above configuration, if an N/D operation isperformed when the vehicle is stopped, the forward first gear is set asthe target gear and one friction engagement element, the C1 clutch 3301,is engaged. However, if the N/D operation is performed while the vehicleis in motion, one of the second to eighth forward gears is set as thetarget gear speed, due to the high vehicle speed V. Therefore, twofriction engagement elements must be engaged as shown in the operationchart of FIG. 3.

According to the present embodiment, if the N/D operation is performedwhile the vehicle is in motion, and two or more (two in the presentembodiment) friction engagement elements must be engaged, at least oneof the friction engagement elements are engaged before the remainingfriction engagement elements.

FIG. 5 shows a functional block diagram of the ECU 8000, which is acontrol device for a vehicle according to the present embodiment. TheECU 8000 includes an input interface 8100, a computation processing unit8200, a storage unit 8300, and an output interface 8400.

The input interface 8100 receives the vehicle speed V from the vehiclespeed sensor 8002, the shift position SP from the position switch 8006,and the accelerator operation amount ACC from the accelerator operationamount sensor 8010, and sends these to the computation processing unit8200.

The storage unit 8300 stores various information and programs, as wellas threshold values and maps that include the above shift diagram. Thestorage unit 8300 reads out and stores data from the computationprocessing unit 8200 as necessary.

The computation processing unit 8200 includes an N/D operation sensor8210, a target gear speed calculation unit 8220, a torque reductioncontrol unit 8230, a first hydraulic control unit 8240, and a secondhydraulic control unit 8250.

The N/D operation sensor 8210 detects an N/ID operation based on theshift position SP.

The target gear calculation unit 8220 calculates the target gear basedon the vehicle speed V, the accelerator operation amount ACC, and theshift diagram when the N/ID operation sensor 8210 detects that an N/Doperation has been performed.

If the accelerator pedal 8008 is depressed between the time fromdetection by the N/D operation sensor 8210 of an N/D operation andformation of the target gear, the torque reduction control unit 8230executes a torque reduction control that adjusts an intake air volume (athrottle opening TH) to reduce the output torque of the engine 1000below a normal value in accordance with the accelerator operation amountACC. Accordingly, the engine torque input to the automatic transmission2000 is decreased, and engagement shock is suppressed. Also note thatthe torque reduction control may be executed by controlling the fuelinjection amount or ignition timing of the engine 1000 in addition to orinstead of the throttle opening TH.

If the target gear speed is the second forward gear or higher, i.e., iftwo friction engagement elements must be engaged to form the target gearspeed, the first hydraulic control unit 8240 outputs the drive currentI, which quickly increases the target command pressure of the firstengagement element, defined in the following paragraph, regardless ofthe input torque, to the solenoid that corresponds to the firstengagement element.

Here, the first engagement element refers to a secondary engagementelement if the target gear speed is not the fifth forward gear, andrefers to the C2 clutch 3302 if the target gear speed is the fifthforward gear. This convention applies in the description below.

For example, if the target gear speed is the second forward gear, thefirst hydraulic control unit 8240 outputs to the SL(5) 4250 the drivecurrent I(B1), which immediately maximizes the target command pressureP(B1) of the B1 brake 3311 to a maximum pressure, namely, the secondaryengagement element that forms the second forward gear.

If the target gear speed is the fifth forward gear, the first hydrauliccontrol unit 8240 outputs to the SL(2) 4220 the drive current I(C2),which quickly increases the target command pressure P(C2) of the C2clutch 3302, namely, one primary engagement element that forms the fifthforward speed. In such case, the first hydraulic control unit 8240 takesinto account that the C2 clutch 3302 is a primary engagement element,and increases the target command pressure. P(C2) in a preset manner toenhance suppression of engagement shock compared to when the targetcommand pressure P(C2) is immediately increased to a maximum pressure.

Once the first engagement element has been engaged by the firsthydraulic control unit 8240, the second hydraulic control unit 8250outputs the drive current I to the solenoid that corresponds to thesecond engagement element so that the target command pressure of thesecond engagement element is gradually increased in accordance with theinput torque.

Here, the second engagement element is another friction engagementelement used with the first engagement element to form the target gear.The second engagement element refers to a primary engagement element ifthe target gear speed is not the fifth forward gear, and refers to theC1 clutch 3301 if the target gear speed is the fifth forward gear. Thisconvention applies in the description below.

For example, if the target gear is the second forward gear, the secondhydraulic control unit 8250 outputs to the SL(1) 4210 the drive currentI(C1), which gradually increases in accordance with the input torque thetarget command pressure P(C1) of the C1 clutch 3301, namely, the primaryengagement element that forms the second forward gear.

If the target gear is the fifth forward speed, the second hydrauliccontrol unit 8250 outputs to the SL(1) 4210 the drive current I(C1),which gradually increases in accordance with the input torque the targetcommand pressure P(C1) of the C1 clutch 3301 that differs from the C2clutch 3302 among the two primary engagement elements that form thefifth forward gear. In the case described above, the second hydrauliccontrol unit 8250 takes into account that the target command pressureP(C2) of the C2 clutch 3302, which is a first engagement element, is notimmediately increased to the maximum pressure, and increases the targetcommand pressure P(Cl) of the C1 clutch 3301 when the target commandpressure P(C2) exceeds a preset hydraulic pressure or after apredetermined time has elapsed since the target command pressure P(C2)started increasing.

When increasing the target command pressure of the second engagementelement, the second hydraulic control unit 8250 executes a quick-applycontrol for a predetermined time to increase the target command pressureto a predetermined hydraulic pressure in order to improve controlresponse. After the quick-apply control, the second hydraulic controlunit 8250 executes a low-pressure standby control to lower the targetcommand pressure to a low standby hydraulic pressure in accordance withthe input torque. After executing the low-pressure standby control, thesecond hydraulic control unit 8250 then executes a sweep control toincrease the target command pressure to a maximum pressure using a sweepamount (an increase amount per unit time) in accordance with the inputtorque. However, the control of the second hydraulic control unit 8250is not limited to this form of control.

According to the present embodiment, the N/D operation sensor 8210, thetarget gear speed calculation unit 8220, the torque reduction controlunit 8320, the first hydraulic control unit 8240, and the secondhydraulic control unit 8250 are all implemented through the execution ofprograms, stored in the storage unit 8300, by a CPU, namely, thecomputation processing unit 8200. In other words, the functions of theunits are implemented through software. However, these units may beimplemented using hardware. Also note that such programs are stored in astorage medium and installed in a vehicle.

A control structure of a program executed by the ECU 8000 will beexplained next with reference to FIG. 6A and FIG. 6B. This program isexecuted at prescribed intervals.

At step (which is abbreviated to “S” below) 100, the ECU 8000 determineswhether an N/D operation has been performed based on the shift positionSP. If an N/D operation has been performed (YES at S100), the processproceeds to S102. If an N/D operation has not been performed (NO atS100), the process ends.

At S102, the ECU 8000 determines the target gear based on the vehiclespeed V, the accelerator operation amount ACC using the shift diagram.

At S104, the ECU 8000 determines whether the target gear is the secondforward gear or higher (i.e., higher than the first forward gear). Ifthe target gear is higher than the first forward gear (YES at S104), theprocess proceeds to S106. If the target gear is not the second forwardgear or higher (NO at S104), the process proceeds to S122.

At S106, the ECU 8000 determines whether the accelerator is depressedbased on the accelerator operation amount ACC. If the accelerator isdepressed (YES at S106), the process proceeds to S108. If theaccelerator is not depressed (NO at S106), the process proceeds to S110.

At S108, the ECU 8000 executes the torque reduction control for theengine 1000 in accordance with the accelerator operation amount ACC.

At S110, the ECU 8000 determines whether the target gear speed is thefifth forward gear. If the target gear speed is the fifth forward gear(YES at S110), the process proceeds to S116. If the target gear speed isnot the fifth forward gear (NO at S110), the process proceeds to S112.

At S112, the ECU 8000 immediately increases the target command pressureof the first engagement element to the maximum value regardless of theinput torque.

At S114, the ECU 8000 gradually increases the target command pressure ofthe second engagement element in accordance with the input torque. Asdescribed above, the ECU 8000 then executes the quick-apply control fora predetermined time. After the quick-apply control, the ECU 8000executes the low-pressure standby control for a predetermined time toreduce the target command pressure to the low standby hydraulic pressurein accordance with the input torque, and after the low-pressure standbycontrol, executes the sweep control to increase the target commandpressure to a maximum pressure using a sweep amount in accordance withthe input torque.

At S116, the ECU 8000 quickly increases the target command pressure ofthe first engagement element (i.e., the target command pressure P(C2) ofthe C2 clutch 3302) in a preset manner regardless of the input torque.The preset manner involves setting an increase period from the start ofincreasing the target command pressure P(C2) until the maximum pressureis reached in advance, and then executing the quick-apply control, thelow-pressure standby control, and the sweep control regardless of theinput torque within the increase period. It should be noted that theincrease period is set shorter than the time from the start ofincreasing the target command pressure of the second engagement elementin accordance with the input torque until the maximum pressure isreached.

At S118, the ECU 8000 determines whether an engagement start conditionof the second engagement element (the C1 clutch 3301) is satisfied. TheECU 8000 determines that the engagement start condition of the secondengagement element is satisfied if the target command pressure P(C2) ofthe C2 clutch 3302 exceeds a prescribed hydraulic pressure, or if apredetermined time has elapsed after the target command pressure P(C2)of the C2 clutch 3302 starts increasing. If the engagement startcondition of the second engagement element is satisfied (YES at S118),the process proceeds to S120. If the engagement start condition is notsatisfied (NO at S118), the process returns to S118 and waits until theengagement start condition of the second engagement element issatisfied.

At S120, the ECU 8000 gradually increases the target command pressure ofthe second engagement element (the C1 clutch 3301) in accordance withthe input torque. As described above, the ECU 8000 then executes thequick-apply control for a predetermined time. After the quick-applycontrol, the ECU 8000 executes the low-pressure standby control for apredetermined time to reduce the target command pressure to the lowstandby hydraulic pressure in accordance with the input torque, andafter the low-pressure standby control, executes the sweep control toincrease the target command pressure to a maximum pressure using a sweepamount in accordance with the input torque. The low standby hydraulicpressure and the sweep amount in this process may be similar to ordifferent from that at S114.

At S122, the ECU 8000 determines whether the accelerator is depressedbased on the accelerator operation amount ACC. If the accelerator isdepressed (YES at S122) the process proceeds to S124. If the acceleratoris not depressed (NO at S124), the process proceeds to S126.

At S124, the ECU 8000 executes the torque reduction control for theengine 1000 in accordance with the accelerator operation amount ACC.This process may be similar to or different from the process at S108.

At S126, the ECU 8000 gradually increases the target command pressureP(C1) of the C1 clutch 3301 in accordance with the input torque. Thisprocess may be similar to or different from the processes at S114 orS120.

The operation of the ECU 8000, which is the control device of a vehicleaccording to the present embodiment, as based on the structure andflowchart described above will be explained next with reference to FIG.7.

This example assumes that an N/D operation is performed and depressesthe accelerator pedal 8008 at a time t(1). In such case, the N/Doperation (YES at S100) is followed by calculation of the target gear(S102). The target gear is then calculated as the second forward gear(YES at S104), and the accelerator is depressed (YES at S106).Therefore, the engine torque is reduced as shown in FIG. 7 (S108).

The description below is divided into an example where the target gearis the second forward gear (i.e., a primary engagement element and asecondary engagement element are engaged to form the target gear) and anexample where the target gear is the fifth forward gear (i.e., twoprimary engagement elements are engaged to form the target gear).

[Second Forward Gear as Target Gear]

The target command pressure P(B1) of the B1 brake 3311, which is a firstengagement element (a secondary engagement element for forming thesecond forward gear), is immediately increased to the maximum pressure(S112), and the target command pressure P(C1) of the C1 clutch 3301,which is a second engagement element (a primary engagement element forforming the second forward gear), is gradually increased using a lowstandby hydraulic pressure and a sweep amount in accordance with theinput torque.

Thus, when a primary engagement element and a secondary engagementelement are engaged, immediately increasing the target command pressureof the secondary engagement element, the engagement of which does notchange the output torque, to the maximum pressure immediately endsengagement of the secondary engagement element. Afterwards, the targetcommand pressure of the primary engagement element, the engagement ofwhich does change the output torque, is gradually increased inaccordance with the input torque in a manner similar to the engagementof one engagement element.

Therefore, a more complex engagement hydraulic control than that used tosimultaneously increase the hydraulic pressure fed to two engagementelements in accordance with the input torque may be avoided. It is alsopossible to suppress fluctuations in the balance between the engagementstate of the primary engagement element and the engagement state of thesecondary engagement element. Consequently, there is no need toexcessively reduce an engine torque reduction amount indicated by adashed line in FIG. 7 in order to suppress engagement shock. Thus, thevehicle is accelerated in accordance with the depression of theaccelerator while suppressing engagement shock, and vehicle travel inline with the driver's intent can be achieved.

[Fifth Forward Gear as Target Gear]

Among the two primary engagement elements used to form the forward fifthspeed, namely, the C1 clutch 3301 and the C2 clutch 3302, first, thetarget command pressure P(C2) of the C2 clutch 3302 is quickly increasedusing a preset low standby hydraulic pressure and a sweep amountunrelated to the input torque (S116).

If the target command pressure P(C2) of the C2 clutch 3302 exceeds thepreset hydraulic pressure at a time t(2) thereafter (YES at S118), thetarget command pressure P(C1) of the remaining C1 clutch 3301 isgradually increased using a low standby hydraulic pressure and a sweepamount in accordance with the input torque.

Thus, if two primary engagement elements must be engaged, one of theprimary engagement elements may be quickly engaged to a degree that doesnot generate shock. When engagement of one of the primary engagementelements is substantially complete, the target command pressure of theother primary engagement element is gradually increased in accordancewith the input torque in a manner similar to the engagement of firstengagement element. Therefore, similar to the engagement of a primaryengagement element and a secondary engagement element, a more complexengagement hydraulic control may be avoided, and acceleration may beachieved in line with the driver's intent while also suppressingengagement shock.

As described above, according to the control device of the presentembodiment, if an N/D operation requires the respective engagement oftwo engagement elements, one of the engagement elements is engagedbefore engagement of the other engagement element. Accordingly,fluctuations in the balance between the engagement state of oneengagement element and the engagement state of the other engagementelement may be suppressed. Thus, even if the accelerator depressedimmediately after the N/D operation, it is possible to suppressengagement shock without excessively reducing the engine torque. Thus,the vehicle may be accelerated in accordance with the depression of theaccelerator while suppressing engagement shock.

The embodiment described herein is intended for purposes of illustrationonly and should not be considered as limiting the scope of the presentinvention. The scope of the present invention is specified by the claimsrather than the above description, and includes any modifications withinthe scope of the claims.

1. A control device for a vehicle, wherein the vehicle includes aplurality of engagement elements that is released when a shift leverposition is in a neutral position; a hydraulic circuit that controls ahydraulic pressure of oil fed to the plurality of engagement elements;and an automatic transmission that changes a speed of and outputs arotation of a drive source, the control device comprising: adetermination unit that determines whether the shift lever position hasbeen changed from the neutral position to a forward running position; atorque reduction unit that controls the drive source such that an outputtorque of the drive source is lower than a torque in accordance with anaccelerator opening, if the determination unit determines that the shiftlever position has been changed to the forward running position; acalculation unit that calculates a target gear speed in accordance witha vehicle speed, if it is determined by the determination unit that theshift lever position has been changed to the forward running position;and a control unit that controls the hydraulic circuit such that a firstengagement element that is part of the two or more engagement elementsis engaged before engagement of a second engagement element, if thetarget gear speed calculated by the calculation unit is a gear speedformed by engaging at least two or more engagement elements.
 2. Thecontrol device according to claim 1, wherein the control unit increasesa hydraulic pressure fed to the first engagement element to apredetermined hydraulic pressure, and then increases a hydraulicpressure fed to the second engagement element.
 3. The control deviceaccording to claim 2, wherein the control unit sets such that a timeelapsed from the when the hydraulic pressure fed to the first engagementelement starts increasing until a maximum pressure is reached is shorterthan a time elapsed from when the hydraulic pressure fed to the secondengagement element starts increasing until a maximum pressure isreached.
 4. The control device according to claim 3, wherein the controlunit increases the hydraulic pressure fed to the first engagementelement regardless of an input torque that is input from the drivesource to the automatic transmission, and increases the hydraulicpressure fed to the second engagement element in accordance with theinput torque.
 5. The control device according to claim 4, wherein if thetwo or more engagement elements are a combination of a primaryengagement element through which the input torque is output from theautomatic transmission even if singly engaged, and a secondaryengagement element through which the input torque from the automatictransmission is not output if singly engaged, the control unitimmediately increases a hydraulic pressure fed to the secondaryengagement element to a maximum pressure regardless of the input torque,and increases a hydraulic pressure fed to the primary engagement elementin accordance with the input torque.
 6. The control device according toclaim 4, wherein if the two or more engagement elements are acombination of primary engagement elements through which the inputtorque is output from the automatic transmission even if singly engaged,the control unit increases a hydraulic pressure fed to part of theprimary engagement elements in a preset manner regardless of the inputtorque, and increases a hydraulic pressure fed to the remaining primaryengagement elements in accordance with the input torque.
 7. A controlmethod for a vehicle, wherein the vehicle includes a plurality ofengagement elements that is released when a shift lever position is in aneutral position; a hydraulic circuit that controls a hydraulic pressureof oil fed to the plurality of engagement elements; and an automatictransmission that changes a speed of and outputs a rotation of a drivesource, the control method comprising: determining whether the shiftlever position has been changed from the neutral position to a forwardrunning position; controlling the drive source such that an outputtorque of the drive source is lower than a torque in accordance with anaccelerator opening, if it is determined that the shift lever positionhas been changed to the forward running position; calculating a targetgear speed in accordance with a vehicle speed, if it is determined thatthe shift lever position has been changed to the forward runningposition; and controlling the hydraulic circuit such that a firstengagement element that is part of the two or more engagement elementsis engaged before engagement of a second engagement element, if thetarget gear speed is a gear speed formed by engaging at least two ormore engagement elements.
 8. The control method according to claim 7,wherein a hydraulic pressure fed to the first engagement element isincreased to a predetermined hydraulic pressure, and then a hydraulicpressure fed to the second engagement element is increased.
 9. Thecontrol method according to claim 8, wherein a time elapsed from thewhen the hydraulic pressure fed to the first engagement element startsincreasing until a maximum pressure is reached is set shorter than atime elapsed from when the hydraulic pressure fed to the secondengagement element starts increasing until a maximum pressure isreached.
 10. The control method according to claim 9, wherein thehydraulic pressure fed to the first engagement element is increasedregardless of an input torque that is input from the drive source to theautomatic transmission, and the hydraulic pressure fed to the secondengagement element is increased in accordance with the input torque. 11.The control method according to claim 10, wherein if the two or moreengagement elements are a combination of a primary engagement elementthrough which the input torque is output from the automatic transmissioneven if singly engaged, and a secondary engagement element through whichthe input torque from the automatic transmission is not output if singlyengaged, a hydraulic pressure fed to the secondary engagement element isimmediately increased to a maximum pressure regardless of the inputtorque, and a hydraulic pressure fed to the primary engagement elementis increased in accordance with the input torque.
 12. The control methodaccording to claim 10, wherein if the two or more engagement elementsare a combination of primary engagement elements through which the inputtorque is output from the automatic transmission even if singly engaged,a hydraulic pressure fed to part of the primary engagement elements isincreased in a preset manner regardless of the input torque, and ahydraulic pressure fed to the remaining primary engagement elements isincreased in accordance with the input torque.